Magnetic carriers for induction-heating ovens



July 19, 1966 H. KOESLING 3,261,448

MAGNETIC CARRIERS FOR INDUCTION-HEATING OVENS Filed Dec. 14, 1964 INVENTOR.

HEINZ KOESLING AGENT United States Patent 3,261,448 MAGNETIC CARRIERS FOR INDUCTION- HEATING ()VENS Heinz Koesling, Notzingen, Germany, assignor to North American Philips Company Inc., New York, N.Y., a corporation of Delaware Filed Dec. 14, 1964, Ser. No. 417,947 Claims priority, application Germany, Dec. 13, 1963, P 33,188 3 Claims. (Cl. 198-41) This invention relates to apparatus for securing workpieces on a transport belt for induction-heating ovens by means of magnetic holding forces.

The use of a known magnetic transport belt involves difiiculties. The workpieces intended to be treated in an induction-heating oven are usually delivered to the oven after having been processed by mechanical tools, during which material which has been removed remains on the workpiece or are attached thereto more or less in the form of burrs. It is a time-consuming operation to clean such workpieces before entering the oven and, if this cleaning is omitted, loose particles of material and those which become loose through the handling of the workpieces are collected at areas where the magnetic field has its strongest concentration and hence substantially on the supporting surfaces of the transport belt. However, cleaning the workpieces does not completely solve this difliculty either, since fixed burrs loosen due to heating of the workpieces and the thin oxide layer produced upon heating, if the workpieces are hardened, are carried onto the transport belt by the cooling liquid.

Due to the unavoidable presence of loose particles of material, the supporting surfaces of the transport belt will be covered to a greater or lesser extent in time. Such particles remain attached to the magnetic supporting surfaces, even after removal of the magnetic energization where electro-magnets are utilized, due to the action of residual remanent magnetism. It is thus unavoidably necessary to carry out the time consuming cleaning operations before workpieces are delivered to the oven.

An object of the invention is to overcome this disadvantage. According to the invention each carrier is provided With at least one pair of inserts of soft magnetic material which is also mechanically resistant to wear. Pole pieces which are permanent magnetic or energized electromagnetically are fixedly arranged on the underside of the transport belt and so that the inserts moving along the pole pieces are thus in the paths of the lines of magnetic force of these pole pieces.

In order that the invention may be readily carried into effect, one embodiment thereof will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawing, in which:

FIGURE 1 is a cross-sectional view of the arrangement, according to the invention.

FIGURE 2 shows a longitudinal section view of the arrangement shown in FIG. 1.

The transport means for workpieces 1 is constituted by carriers 2 which together form a chain or belt and are provided with rollers 3 which support the carriers 3,261,448 Patented July 19, 1966 2 on tracks 4. Each carrier has at least one pair of inserts 5 of soft magnetic material so that, after magnetic energization, the residual remanent magnetism is very weak. With regard to the mechanical strength the material is required to have a high resistivity to wear.

Magnet poles 6 and 7 of opposite polarity, which are separated by a wall 8 of non-magnetic material, are provided on the underside of the transport member. The said poles 6 and 7 may form part of a permanent magnet or be magnetized electrically. The inserts 5 are separated from the poles by a narrow gap 9. When a workpiece 1 supported on the carriers 2 has been brought Within the reach of the magnetic field between the poles 6 and 7 and inserts 5 act as magnetic conductors for the magnetic flux 10 which passes through the workpiece. The workpiece 1 is thus clamped in position by virtue of the magnetic field and, in order to ensure good contact between the workpiece and the inserts, the latter preferably project slightly above the surfaces 11 of the carriers 2.

As the inserts move with the carriers, they come successively to areas where no magnets 6 and 7 exist so that the magnetic flux disappears and the inserts, because of their extremely low remanence, are substantially nonmagnetized so that even small dust particles no longer keep adhering. The supporting surfaces 12 of the inserts 5 are thus kept free of particles and may be used again for a subsequent transport of workpieces without further cleaning operations. A material suitable for manufacturing the inserts is the known ferrite.

FIGURES 1 and 2 are not intended to be representative of a rectilinear transport belt. With the use of the invention the transport of workingpieces may take place as well on paths which are, for example, circular or of other curvature.

What is claimed is:

1. Apparatus for the transport of workpieces in induction-heating ovens comprising a transport belt having a plurality of carriers, at least one pair of inserts of soft magnetic material for each said carrier and discrete magnetized pole pieces fixedly arranged with respect to said carriers along the underside of said belt, whereby said inserts are alternatively magnetized and de-magnetized when the transport belt is operative.

2. Apparatus according to claim 1, wherein said inserts project above the surfaces of said carriers.

3. Apparatus according to claim 1 wherein said inserts consist of ferrite material.

References Cited by the Examiner UNITED STATES PATENTS 2,526,253 10/1960 Merrill 198-41 FOREIGN PATENTS 12,148 12/1955 Germany.

EVON C. BLUNK, Primary Examiner. R. E. KRISHER, Assistant Examiner. 

1. APPARATUS FOR THE TRANSPORT OF WORKPIECES IN INDUCTION-HEATING OVENS COMPRISING A TRANSPORT BELT HAVING A PLURALITY OF CARRIERS, AT LEAST ONE PAIR OF INSERTS OF SOFT MAGNETIC MATERIAL FOR EACH SAID CARRIER AND DISCRETE MAGNETIZED POLE PIECES FIXEDLY ARRANGED WITH RESPECT TO SAID CARRIERS ALONG THE UNDERSIDE OF SAID BELT, WHEREBY SAID INSERTS ARE ALTERNATIVELY MAGNETIZED AND DE-MAGNETIZED WHEN THE TRANSPORT BELT IS OPERATIVE. 